The use of pyridinethione salts as antidandruff agents in shampoos and hair rinses is well known. U.S. Pat. No. 3,236,733, Feb. 22, 1966 to Karsten et al discloses detergent compositions containing such salts. Barnett, B. L., et al, "Structural Characterization of Bis(N-oxypyridine-2-thionato)Zinc(II)," Inorganic Chemistry, 16, 1834, [1977] discloses recrystallizing zinc pyridinethione crystals from chloroform or dimethyl sulfoxide. Other references which disclose pyridinethione salts are U.S. Pat. No. 2,809,971, Oct. 15, 1957 to Bernstein et al; U.S. Pat. No. 3,723,325, Mar. 27, 1973 to Parran; U.S. Pat. No. 3,753,916, Aug. 21, 1973 to Parran; U.S. Pat. No. 3,761,417, Sept. 25, 1973 to Parran; and U.S. Pat. No. 3,761,418, Sept. 24, 1973 to Parran.
While it is known to use pyridinethione salts in hair care compositions the prior art does not indicate whether the salts are compatible with all components which may be present in a composition. Included among components which may be present in shampoos and other hair care compositions are those which make the compositions more aesthetically appealing. Aesthetics are important in encouraging a consumer to purchase a product as well as continue using the product after purchase.
One aesthetic characteristic which has found wide acceptance is pearlescence. This is quite often achieved through the use of material such as ethylene glycol distearate. The pyridinethione salt materials available up to this time have substantially interfered with the ability of pearlescent material to deliver acceptable pearlescence. This has been due, in all likelihood, to the materials being in the shape of cubes and rods and of small size. The recrystallized material of Barnett et al supra, while allowing pearlescence, has been found to be less acceptable than the crystals of the present invention in finished compositions.
It is therefore an object of the present invention to provide pyridinethione salt crystals which interfere less with the pearlescent material than do prior art materials.
It is another object of the present invention to provide antidandruff compositions containing such crystals.
These and other objects will become obvious from the detailed description which follows.